[llvm] [VPlan] Simplify the computation of the block entry mask. (PR #173265)

[Mel Chen via llvm-commits]

================
@@ -128,16 +137,38 @@ VPValue *VPPredicator::createEdgeMask(VPBasicBlock *Src, VPBasicBlock *Dst) {
   return setEdgeMask(Src, Dst, EdgeMask);
 }
 
-VPValue *VPPredicator::createBlockInMask(VPBasicBlock *VPBB) {
+void VPPredicator::createIncomingEdgeMasks(VPBasicBlock *VPBB) {
   // Start inserting after the block's phis, which be replaced by blends later.
   Builder.setInsertPoint(VPBB, VPBB->getFirstNonPhi());
+  for (auto *Predecessor : SetVector<VPBlockBase *>(
+           VPBB->getPredecessors().begin(), VPBB->getPredecessors().end()))
+    createEdgeMask(cast<VPBasicBlock>(Predecessor), VPBB);
+}
+
+VPValue *VPPredicator::createBlockInMask(VPBasicBlock *VPBB) {
   // All-one mask is modelled as no-mask following the convention for masked
   // load/store/gather/scatter. Initialize BlockMask to no-mask.
   VPValue *BlockMask = nullptr;
+
+  // TODO: Skip creating edge masks for blocks that are control-flow equivalent
+  // to header and have no phis.
+  createIncomingEdgeMasks(VPBB);
----------------
Mel-Chen wrote:

c28ff7fad709bf7ebc9376f0abb8a27d2df568bf

https://github.com/llvm/llvm-project/pull/173265